Forecasters: (NWS) and Clay Morgan (NWS)
Low level moisture has returned to the STEPS region, with surface dew points ranging from the mid 50's in the western edge of the domain to mid 60's on the east. Dew points are forecast to remain in the mid-to-upper 50's after surface heating mixes the moisture through the boundary layer, with a dry line setting up in the western portion of the domain by early afternoon. East of the dry line, CAPEs will reach 2000 j/kg or greater, offering the potential for severe convection with hail up to 1 inch possible in some of the cells. Triggering will be enhanced by a weak upper-level disturbance propagating through the region this afternoon and evening. However, vertical wind shears will be too weak for supercellular activity.
Conditions for Friday will be very similar to today, with a continued chance of svere convection. However, shear values will remain weak.
For Saturday, the low-level moisture and instability will remain in place, with an approaching upper-level wave and associated surface cold front enhancing the triggering potential as well as vertical wind shear magnitudes. An issue for Saturdays' possibilities is the forecast timing for frontal passage, which is currently early afternoon, potentially too early for severe convection to develop within the research area.
| VARIABLE | Day 1: 1-4 pm | Day 1: 4-9 pm | Day 2 | Day 3 |
|---|---|---|---|---|
| Convective Potential |
2 | 3 | 3 | 3 |
| Storm Type | 1 | 1 | 1 | 2 |
| Triggering | 1 | 2 | 1 | 2 |
| Intuition | 0.5 | 1 | 1 | 0 |
| Total | 4.5 | 7 | 6 | 7 |
| SYSTEM | STATUS |
|---|---|
| Ops Center | Operational. |
| CHILL | Operational. |
| S-Pol | Operational. |
| LMA | Operational. |
| MGLASS | Operational. |
| T-28 | Operational. |
| Storm ballooning | Operational. |
| Mobile mesonet | Single vehicle with the rest unavailable since no supercells are expected. |
| Storm chase van | Operational as the primary precipitation verification vehicle. |
| YRFS | Operational. |
| NWS | Operational. |
Radars are requested to be up by 1:00pm, with mobile units on standby for 2:00pm. MGLASS soundings will be taken at 19 UTC in Stratton CO and Colby KS, with soundings also possible at these locations at 00 UTC.
Electric ballooning units will only deploy soundings today in storms with large hail (~1 in) or exhibiting dominant positive CGs. A single mobile mesonet and the hailstone van will be used for ground-truth verification of precipitation types.
Operations first concentrated on a severe cell centered in the western Doppler lobe as of 5pm MDT. This cell was at the southern end of a well organized MCS and was exhibiting a predominance of positive CGs. The original target cell collided with another severe cell that had moved northward from the Burlington area between 6:00 and 6:30 pm. This resultant storm complex then moved towards the east-northeast over the S-Pol radar site. Up to 1 inch hail was reported with these cells along with surface winds up to 30 m/s and a brief, weak tornado 4 miles west of Idalia about 6pm.
The T28 was called out at 5pm along with the storm intercept and the mobile ballooning units, which were vectored to near Idalia for soundings and ground verification. The T28 did transects of the storm system between 5:50 and 6:50 pm, experiencing significant turbulence, icing, hail, and frequent lightning. An initial tandem electric balloon was launched into the updraft, but failed as the instrument package separated from the balloon shortly after launch. Two successful balloon launches were obtained on the western side of the storm system. The lightning mapping network showed a large positive charge layer within the storm at heights between 6 and 9 km. Radars continued coordinated scans of the system through about 9pm, as it moved northeast of the Goodland area, within the eastern dual-Doppler lobe.